1. Technical Field
This invention relates to golf clubs. It further relates to the aerodynamic shaping of the head of a golf club. It relates still further to an aerodynamically streamlined golf club made by the combination of a faceplate fixed to an aerodynamic fairing.
2. Description of the Prior Art
Golfe' is noted in a decree of the Scottish parliament under James II dated March 1457 at which time people seemed to be playing too much golf at the expense of their skill at bowemerkis (archery). In 1471, another decree under James III was passed to discourage golfe and futeball and in 1491 King James IV issued a decree with pains and penalties attached wherein "Futeball and Golfe Forbidden" because he decided it was degrading Scotland's level of defense preparedness against the threat of invasion by England. Shortly afterwards, James IV shifted his defense budget from the Bowers Guild to the Alchemists and the fire arms makers, and then legalized golf once again so that the suddenly unemployed Bowers could now make and sell golf clubs and support their families.
Throughout five centuries of recorded golf history, one reads of occasional conflict, usually driven by social or technological forces independent of the game. A current minor example of conflict in golf equipment utility can be found in the needs and desires of manufacturers to generate profits in juxtaposition to the desire of golf's regulating bodies to maintain the game. The development of new golf equipment has been slow during the 20th century as most of the world's scientists and engineers have taken defense related research jobs. Industries such as golf whose products relate to leisure have been unable to compete as the brightest people were employed elsewhere while leisure equipment has been left behind.
Golf clubs, to be allowed for use in tournament and competition play, must conform to the rules of The United States Golf Association (U.S.G.A.) founded in 1894 and The Royal and Ancients Golf Club (R & A, and also known as the R.A.G.C.) of St. Andrews, Scotland founded in 1754. These two groups together form the traditional regulating body governing the rules of golf and its equipment. In this capacity, the U.S.G.A. and the R & A will on occasion accept an advance in science or technology and permit the application of such to the making of a change in club or ball manufacture when in their judgement they believe such change will benefit the spirit and traditions and customs of golf.
Notable changes brought on by technology are illustrated by the development of the golf ball. The earliest known ball was the "feather", a hatful of feathers packed into a sewn up leather cover. The best player could hit a feather about 150 yards. In 1848, the "guttie" was introduced, a smooth ball made of rubbery gutta-percha which could be hit about 195 yards. A new guttie would duck and twist erratically in flight but performed better and better as it became scarred and rough. It was accordingly modified by players to make it rough and then by manufacturers who added dimples that made the flight path more predictable. In 1898, a rubber cored ball was introduced that gave a more precise trajectory than the guttie and could be hit about 255 yards by a good player. The rubber ball was more reliable in play, the guttie having had the perplexing tendency to fly into several pieces when played.
To limit the ingenuity of golf ball manufacturers, the U.S.G.A. introduced a machine in 1941 to automatically play the ball. A ball at a temperature of 23 +/-1 degree C. must not leave the machine at greater than 250 feet per second. The average distance a ball will travel in carry and roll, when driven by a standardized machine, is now limited to 280 yards.
Not all technical "improvements" have been acceptable. Several manufacturers marketed recently a new golf ball that once again improved the range obtainable with a normal drive. On this occasion, the regulating bodies judged it to be not in the best interests of the traditions and nature of golf and determined that the new ball does not conform to the rules.
Golf clubs have gone through a similar technical transition. The earliest known clubs had a wooden head fitted to a wooden shaft. In 1929, use of the steel shaft was sanctioned by the R.A.G.C. and the U.S.G.A. The head of the "wood" was then changed to a hollow steel shell, and now is permitted in a variety of metals as well as fiber reinforced plastic, the core frequently being filled with a foam plastic. The shaft may also be composed of a fiber reinforced plastic composite.
In the area of aerodynamics as applied to the golf club, some research has been done and several patents have been granted for clubs claimed to have reduced aerodynamic drag whereby the golfer can attain increased swing speed and an increased distance for the golf ball. U.S. Pat. No. 5,190,289 by Nagai et al describes the use of a wind tunnel to measure drag on a golf club. Factors such as lift and pitching moment were not mentioned however and the improvement in performance was cited as 3%.
Air resistance and drag is mentioned in U.S. Pat. No. 5,398,935 by Katayama which shows an aerodynamic shape, but does not address the changing forces as the clubhead rotates.
Iriarte in U.S. Pat. No. 5,435,558 shows a design with two channels as cavities that direct the airflow alongside the clubhead to give stabilization and minimize undesired vibration.
Davis et al in U.S. Pat. No. 5,318,297 add airfoils to stabilize and smooth out airflows on a clubhead, but in no manner would the inventions of Iriarte or Davis et al conform to the U.S.G.A. rules as they are now interpreted.
In U.S. Pat. No. 5,092,599 Okumoto et al show a spoiler on the clubhead that distorts and changes the airflow on the clubhead, but for only one specified direction of club motion.
In U.S. Pat. No. 2,447,967, Stone covered the problem of the different characteristics between the two types of clubs known as "woods" and "irons", and he attempts to improve upon this ergonomic and aerodynamic problem. His solution is based upon vibration, mechanical commonality, visual factors, and materials available. The result was a slight improvement in the aerodynamic lift characteristics of his club set.
No prior art was found regarding the problem of air flow over the clubhead as the club rotates, during a golfer's swing, about the longitudinal axis of the shaft.
The Wright brothers historic flight in 1903 and their subsequent patent showed the principle of aerodynamic lift forces through their careful study of aerodynamics as it could be applied to the shape, form, and fashion of their invention. These aerodynamic forces now affect a considerable portion of mankinds' activity and yet they are not yet utilized in the design of golf clubs.
In this invention, two aerodynamic problems of woods golf clubs were studied. The first of these problems is that of "lift" or "dive force acting on the club. In a series of tests run at Georgia Institute of Technology, School of Aerospace Engineering in their Low Turbulence Wind Tunnel, it was found that a Spalding 2 wood generated 0.144 pounds of lift directed along the axis of the shaft towards the grip at a freestream air speed of 70 feet per second flowing perpendicular to the clubface. This velocity is approximately 40% of that achieved by the professional golfer so the lift force in actual use of a club is over five times this value or approximately 0.75 pounds. Similar tests made on a Wilson 4 iron showed 0.27 pounds of lift, corresponding to approximately 1.35 pounds lift at peak swing speed.
Tests comparing other woods and irons have shown that most irons exhibit a diving force while typical woods exhibits a lifting force. This strong difference between woods and irons can of course confuse the casual golfer as he switches between say a five wood and a number one iron. The difference between the wood and the iron is really only controllable by the dedicated or professional golfer who practices driving and plays golf often enough to learn how to compensate for the differing eccentricities between his clubs.
A second aerodynamic problem occurs in golf clubs. This is that during the common golf swing of a wood or an iron, the club shaft is rotated by 90 degrees or more and in many cases as much as 135 degrees about its longitudinal axis during the 90 degrees of swing prior to striking the ball. During this same portion of the swing, the club is accelerated from approximately 65 miles per hour (MPH) to over 100 MPH, and in the case of a professional golfer, to as high as 140 MPH. Add to this the fact that golf is frequently carried on when winds or wind gusts may exceed 30 MPH, this velocity being added or subtracted from the swing velocity according to the direction of ambient wind past the golfer.
This means that airflow over the club flows from the heel to the toe when the shaft is horizontal (at 90 degrees prior to impact) and has shifted to flow from the face to the back of the clubhead when the club is reaching impact.
Another factor to consider in a study of aerodynamic effects on the clubhead is that a blunt clubhead will generate von Karman vortices behind it when traveling at these speeds. Such vortices grow in size and follow behind the clubhead, then break away only to be immediately followed by growth of a new vortex of opposite rotational direction which repeats the process.
The problem with such vortices is twofold. First, the alternating vortices create an oscillating force on the body which is generally perpendicular to the direction of air flow and which may equal or even exceed the magnitude of the previously mentioned lift forces. In this case the oscillating force will operate in the same direction as the maximum component of the lift/dive forces. Such an oscillating force on the clubhead when it is only supported by a limber shaft can cause it to deviate from its non-perturbed flight path and cause a poor shot or even a miss altogether.
The second problem is that these vortices indicate that a high drag factor is operating. Such drag of course will decrease club speed and diminish the distance obtained with the ball.